Photographic-printing apparatus



July 12,1927.

5. L. LEBBY PHOTOGRAPHIC PRINTING APPARATUS Filed Dec. 19, 1922 INVENTOR S Lee L655 BY J 'I M W ATTORNEY Patented July 12, 192?;

- "Umrs" wean r noroeaermc-ramrme arraaa'rus.

Application filed December, ieaa. serial mi. 001,845.-

The prime object of the invention is to provide a novel electric circuit for photographic printing apparatus, the circuit being so arrangedthat the lamps of the apparatus a will beprotected from so called burn-outs resulting from constant relighting-in making the exposures to the prints.

. In the accompanying drawing wherein is illustrated the preferred embodiment of my 1.0 invention; the figure is a horizontal section through .the photographic printing appa-' ratus with the top removed and showing the lighting circuit when the apparatus is ready to make exposures.

he apparatus comprises a rectangular box 5, which may be ofany convenient-size. In the center of one end wall 6, of the box, I secure an ordina socket 7, while near one end of one of the sides 8 of the box, I secure 20 another-socket 9. By preference the socket 7-carries a high candlepower exposure lamp 10, while the socket 9 carries a low candlepower ruby lamp 11, the lamp 11 having about one fourth the candlepower of the Z5 lamp 10, as is one-rally the practice in apparatus of this aracter.

Conductors 12 and 13 entering the side 6 of the box from the exterior, are res ectively connected to the sockets 7 and 9. on-

.30 necting the socket 7 to the socket 9-is another conductor 14. This arrangement of the light circuit is such that the lamps 10 and 11 are connected in series, and will both be simultaneously supplied with current as from the conductors 12 and 13. A switch 15 can be secured tothe conductors 12 and 13 beyond the box to serve as means of breaking the circuit when the apparatus is not in use, or the usual attachment cord and plug w may be used instead.

When the apparatus is connected to the circuit for use, the ruby lamp 11 will burn at nearly normal brilliancy and the current, which is also passing through the exposure lamp 10 will keep the filament of the latter at a glow, or warmed up.

Now in order to short circuit the ruby lamp 11 and allow the full line voltage to pass through the efxposure lamp 10, I utilize w a simple push-button switch 16 which has one terminal connected to the conductor 14, between the sockets 7 and 9, by means of a conductor 17, and its other terminal connected to the conductor 13, by means of a .11 back to nearly normal candlepower. At

conductor 18. This push-button may' be 55 actuated by being manually depressed.

When the apparatus is in use and assum ing that the operator is positioning a negag tive and sensitized, paper in the printin frame (not shown), the current of the f I toline voltage, will, in passing through the circuit, impart a slight glow to the filament of the ex osure lamp 10. This glow is hardly noticeable to the eye, and hence will not be of sufiicient brilliancy to prove detrimental to the proper functioning of the apparatus while the filament of the ruby lamp 11 will urn at nearl normal brilliancy;

Assuming that t e operator wishes to. make an exposure, the push-button 16, upon being depressed, will cause the lamp 11 to be short-circuited, thereby increasing the current to lam 10, and thus bring the lamp 10 to full bri iancy.

Upon releasing the push-button 16, the filament of the exposure lamp -10 gradually drops in temperature and thus decreasing in resistance, gradually brings the ruby lamp the same time the small amount of voltage retained by the exposure lamp 10 from the ruby lamp 11, for keeping the filament of lamp 10 warmed-up, further increases the life of the ruby lamp 11.

Thus this method of relighting the ruby lamp 11, provides what may be termed, an automatic heat rheostat in lamp 10, which at the moment of releasing the push-button 16, gradually de-energizes, and in cooling, gradually lowers in resistance, forcing its voltage to the lam 11 which is the higher resistance unit of t e circuit.

Heretofore, so far as I am aware, it has been the custom to provide independent switches, or a double-t row switch for the lamps, That is to say,-the apparatus now in general use are composed of two electric circuits, the exposure lamps being on one circuit, while the safe light, or ruby lamp is on th'e'other circuit, it being necessary for the operator to switch from one circuit to the other, when making consecutive exposures.

' This constant switching on of electric incandescent lamps roduces a sudden rise in the temperature 0 the cold lamp that tends to fracture or burn out the filament, dueto the very sudden expansion of the several brittle parts thereof, and it has been proven that it is generally the case that incandescent lam s burn out at the moment of lighting.

Thu

s by my invention the high candlepower ex osure lamps and the low candlepower rub lamps are controllable from a single pus -button switch, which 1s so arranged with respect to the light circuit that the function of both lamps are controlled thereby. Furthermore, the'filaments of both lam s will at all times be protected from sudden thrusts of the entire line voltage, and therefore the loss of the lamps through burnouts is overcome.

Having thus described'my invention what I claim is v a g A device of the class described comprisin an electric circuit having two lamps, one 0 said lamps being clear and the other lamp being ruby, said rub lamp having relatively eater resistance t an the clear lamp and 'eing capable of carrying suflicient current to cause'subdued illumination of the clear lamp, a switch, and circuit connections for connecting the source of current, and the switch in arallel with the ruby lamp, whereb the ru lamp can be short circuited to a low the ullline voltage to pass through the clear lamp andthe clear lamp can function as an automatic heat rheostat when the ruby lamp is lighted. v

In testimony whereof, I hereunto sign my name;

STATES LEE LEBBY. u 

